The weft feeding devices for weaving looms or for textile machines in general (also briefly called weft feeders), now used on all modern shuttleless looms, are usually of the type with a drum for weft yarn storage, incorporating a coaxial electric motor. The weft yarn, unwound from a reel or bobbin, is wound in turns by a rotor on the drum, so as to form a reserve thereon, from which the loom subsequently draws the weft yarn with a tension being as uniform and as regular as possible.
The overall structure most commonly adopted by constructors for these devices comprises a casing formed of a central body housing the electric motor and of a peripheral arm rigidly connected to the central body and supporting a weft yarn brake unit, a sensor detecting the amount of yarn wound on the drum, and a yarnguide eyelet.
The central body of the device is required to have a proper rigidity and high thermal dissipation properties, while the peripheral arm, as well as being suitably stiff, should also act as a sliding and support guide for the brake unit, for the sensor detecting the yarn reserve and for the yarnguide, these members having to be easily movable longitudinally along the arm, so as to control the strength of the braking action on the yarn being fed from the device and, respectively, the yarn reserve being stored on the drum.
The main longitudinal axis of the device corresponds to the motor and drum axes, while the longitudinal axis of the sliding guide should be parallel to the main axis, so as to always allow proper alignment of the brake unit and of the detector in respect of the remaining part of the device.
To satisfy these requirements, in the casings of known weft feeders, the central body is conventionally obtained by casting of aluminum or "zamak" (or other alloy) and, for large production quantities, diecasting is obviously adopted, involving considerable investments for the casting equipment.
As concerns the peripheral support and guiding arm, it should be rigidly fixed to the central body and can be made from different materials and using different methods, for instance by casting of aluminium, zamak or other alloys (adopting diecasting for large quantities of pieces), with the sliding guides incorporated into the arm and eventually obtained by subsequent machining, or made of stamped iron plate or extruded bar and performing simultaneously the dual function of support and guide, or made of section iron or of a similar material with the sliding guides obtained by machining, or finally also obtained by simultaneously adopting two or more of these systems, like associating a secion iron as support with an aluminium extrusion as sliding guide.
In any case, all these systems require a proper fixing between the various parts forming the casing, as well as supplementary machinings which are often neither simple nor economical.
Furthermore, to give a pleasant aspect to the weft feeder, one usually provides for surface finishings, like varnishing and/or applying closing and finishing elements, generally of plastic material, these steps involving costs and structural complications which should well be taken into consideration.